Draft gear assemblies for cushioning buff and draft shocks encountered during make-up and operation of a railway vehicle are well known in the art to include a housing having a closed end and an open end, a compressible member disposed within the closed end and a friction mechanism disposed within the open end. A representative teaching of prior art friction clutch mechanisms can be found in U.S. Pat. Nos. 2,916,163; 3,178,036; 3,447,693; 4,556,678; 4,576,295; 4,591,059; 4,645,187; 4,735,328; 5,152,409; 5,351,844; 5,529,194; 5,590,797; 6,478,173; 6,488,162; 6,520,360 and 7,264,130. Most, if not all, of these prior art type draft gear assemblies either have been or still are being utilized in the railway industry prior to the development of the present invention. Furthermore, except for U.S. Pat. Nos. 4,576,295; 4,591,059; 4,735,328 5,351,844; 6,478,173; 6,488,162; and 6,520,360, each of the remaining above-identified patents is owned by the assignee of the present invention. The teachings of each of the above-referenced patents are incorporated herein by reference thereto.
Lately, various railroads and operators of railway vehicles have been seeking to increase loading capacity of the railway vehicles, such as freight cars, and increase the capability of the draft gear assembly to withstand higher dynamic impact forces.
In an attempt to accommodate such increased loading capacity and to withstand higher dynamic impact forces, the compressible member has been provided as a stack of elastomeric pads separated by plates. The pads and plates are positioned transversely to the longitudinal axis of the housing. Each pad is compressed along the longitudinal central axis toward the rear of the draft gear to cushion the buff dynamic impact forces (shocks) and is compressed along the same longitudinal axis toward the front of the draft gear to cushion the draft dynamic impact forces (shocks). During pad compression, each plate moves along the longitudinal axis during cushioning the buff and draft dynamic impact forces (shocks). The pad is manufactured from either from a thermoset material such as rubber or from a thermoplastic copolyester material. Copolyester material manufactured under Hytrel brand by DuPont de Numerous is a common material in the draft gear art.
U.S. Pat. No. 6,520,360 issued to Withall et al. and U.S. Pat. No. 6,478,173 issued to Carlstedt disclose one type of such draft gear assembly wherein a pair of adjacent pads is separated by a plate and wherein a center rod is provided and is mounted through apertures formed in each plate and pad.
U.S. Pat. Nos. 6,488,162 and 5,351,844, both issued to Carlstedt, disclose another type of such draft gear assemblies wherein each pad is disposed between a pair of plates.
The teachings of each of the above-referenced patents are incorporated herein by reference thereto.
While such devices have acceptable energy absorption capacities, the use of a center rod independently or in combination with additional plates increases both the weight and cost of the draft gear assemblies.
Therefore, there is a continuing need for a lightweight and cost effective draft gear employing compressible elastomeric spring and capable of withstanding a higher impact forces during cushioning of buff and draft dynamic impact forces (shocks).